Sérgio Romano Signorini

A Note on the Transport of the Brazil Current

Abstract An XBT survey and hydrographic sections between 19 and 25°S along the coast of Brazil in April of 1982 were used to locate the Brazil Current both north and south of the seamount chain at 20°30′S. The current appears to flow through the passage between the most inshore of the banks and not to the east. It is a continuous feature and, to the extent resolved by these measurements, is not characterized by meanders and eddies at these latitudes. Transport relative to 500 m (1000 m) was approximately 3.8 × 106 m3 s−1 (6.8 × 106 m3 s−1) and did not appear to increase downstream.

Physical and chemical aspects of transient stages of the upwelling at southwest of Cabo Frio (Lat. 23ºS - Long. 42ºW)

As observacoes oceanograficas realizadas em fevereiro de 1971, na plataforma continental entre Cabo Frio e a Ponta de Guaratiba, mostraram a presenca e a atenuacao de efeitos do fenomeno de ressurgencia observados na superficie. A analise detalhada da distribuicao termica na camada superficial evidencia que o processo fisico responsavel pela atenuacao desse fenomeno foi a adveccao de uma corrente costeira de aguas quentes, fluindo para leste. A componente zonal dessa corrente costeira atingiu nas proximidades da costa o valor maximo de 5 mn. dia 1 e a sua intensidade decresceu com o aumento da distancia a costa, anulando-se aproximadamente sobre a isobata de 100 m. Os efeitos do fenomeno de ressurgencia na superficie, observados ao largo da Ponta de Saquarema, eram claramente indicados pelos minimos de temperatura (17oC) e da concentracao de oxigenio dissolvido (4,2 ml/l) bem como pelo maximo na concentracao de fosfato (0,6 µg-at/l), que sao caracteristicos de aguas mais profundas. No intervalo de tempo (4-7 dias) decorrido entre as observacoes, verificou-se nao somente aumentos de temperatura e do oxigenio dissolvido, como tambem um decrescimo na concentracao de fosfatos de aproximadamente 50% de seu valor inicial.

A study of the circulation in Bay of Ilha Grande and Bay of Sepetiba: part II: an assessment to the tidally and wind-driven circulation using a finite element numerical model

A finite element, two-dimensional hydrodynamical numerical model developed by Wang & White (1976) was applied to study the tidal and wind-driven rculations in the coastal domain formed by Bay of Ilha Grande and Bay of Sepetiba. The tidal circulation was modeled by imposing a co-oscillating tidal signal at the open boundaries of the domain. The amplitude and phase of the tidal constipants adopted to run the numerical experiment were based on harmonic analysis of previous investigations in the region, plus data obtained from two tide gauges ins tailed near the open boundaries of the modeled domain. The numerical simulation of the wind-driven circulation was based on wind data statistics covering 16 months of data. The effect of the wind in the local circulation was weighted by the frequency distribution of wind directions as well as the associated most probable wind forces. The numerical model was also used to simulate seiche oscillations in the coupled system formed by Bay of Ilha Grande and Bay of Sepetiba. The model results are in agreement with the results derived in Part I of this paper, where field data was analysed and discussed.

Contribuição ao estudo da circulação e do transporte de volume da corrente do Brasil entre o Cabo de São Tomé e a Baía de Guanabara

During the periods of April, July, 1970 and July, 1973, oceanographic cruises were conducted in order to investigate the variability of the Brazil Current in the region between Cabo de Sao Tome and Guanabara Bay. The geostrophic model of ocean circulation was applied using the hydrographie data collected during the cruise. From this study, a maximum velocity of 70 cm/sec and a volume trans port of 14 x 106 m3/sec were reported. The dynamic topography with reference to the 500 db surface, showed the presence of anticyclonic eddies during the periods of April, 1970, and July, 1973. The thermohaline structure within a meander of the Brazil Current is also presented utilizing the data coming from a continuous salinity and temperature recorder in conection with the data coming from a simultaneous BT section.

Tidal and Low-Frequency Currents Near the Shelf-Break: Northeastern Coast of Brazil

Abstract Time series of a 40-day (13 March-23 April 1979) wind and current observational experiment are analyzed. The wind data originated from the Fortaleza Airport Weather Station (Ceara, Brazil), and the current meter data originated concurrently from moorings deployed on the shelf break, 40 km offshore. The meters were placed at 8, 16 and 36 m. Strong tidal currents were observed, with a range of 30 to 40 cm s−1 during the equinoctial spring tide period. The analytical model of Battisti and Clarke was applied to the prediction of the diurnal and semidiurnal tidal currents at the mooring site. Good overall agreement with the data was obtained. The wind record spectral and harmonic analysis indicated the presence of a relatively strong diurnal breeze (amplitude of 2.2 m s−1) and a less energetic semidiurnal breeze (amplitude of 0.9 m s−1). A low frequency coastal current flowing northwestward with a near surface mean speed of 16 cm s−1 was also observed. Alongshelf wind and current are highly coherent i...